1. Field of the Invention
The present invention relates to a method for converting A/D and an A/D converting apparatus for converting an analog signal into a digital signal. The present application claims the benefit of, and priority to, Japanese patent application No. 2004-163704 filed on Jun. 1, 2004, the entire contents of which are incorporated herein by reference for all purposes.
2. Description of the Related Art
Conventionally, in order to increase an apparent sampling rate in case of converting an analog signal into a digital signal, a N-way interleave a method for converting A/D using N analog-to-digital converters (hereinafter, referred to “ADC”) was known (For example, see Japanese Laid-open patent application 2000-346913).
However, for the above mentioned interleave a method for converting A/D, if there are errors in the phase of a sampling clock applied to each ADC and the frequency characteristic of each ADC, it is impossible to acquire a frequency spectrum of the digital signal precisely.
For example, although the phase of each sampling clock applied to each ADC needs to be different by a predetermined phase from each other, it is difficult to shift the phase of each sampling clock by the predetermined phase precisely. Further, even when a sampling clock is applied to each ADC with a correct phase, if the frequency characteristic of the ADC is not ideal, fluctuations occur in the sampling timing and gain of each ADC and it is difficult to acquire the frequency spectrum of the digital signal precisely.
Accordingly, an object of the present invention is to provide an interleave AD converting method and an interleave AD converting apparatus, which are capable of overcoming the above drawbacks accompanying the conventional art. The above object can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.